1. Field of the Invention
The invention relates to a structural frame for a turbomachine, such as in particular a fan frame, an intermediate frame, or an exhaust frame, and it also relates to a turbomachine including a frame of this type.
2. Description of the Related Art
In a turbomachine, such as an airplane turbojet, structural frames are arranged along the drive axis in order to stiffen the turbomachine, in order to avoid distortion of the turbomachine, and thereby transmit thrust forces better to the airplane to which the turbomachine is fastened. By way of example, such structural frames are the intermediate frame and the exhaust frame. The intermediate frame is situated between the low and high pressure compressors, and the exhaust frame is located downstream from a turbine section arranged at the outlet from a combustion chamber.
This type of frame is generally made up at least two coaxial rings, an inner and an outer ring, the inner ring defining the inside of a flow passage for a primary air stream flowing through the turbojet, and the outer ring defining the outside of a flow passage for a secondary air stream that flows outside the turbojet. The inner and outer rings are connected together by arms extending radially through the primary and secondary air streams. An intermediate ring is interposed between the inner and outer rings, it has the arms passing therethrough, and it defines the outside of the passage for the primary stream.
These frames are generally made as one-piece castings. It is also known to make the inner ring, the intermediate ring, and the radial arms as a single piece and then to weld the single-piece outer ring to the radial arms.
Nevertheless, making that type of structural frame becomes increasingly complicated and expensive with increasing diameter of the frame. Furthermore, after casting, lengthy and complex machining operations need to be performed on the outer ring where it has junctions with the arms in order to form tubular projections at those junctions for passing services into the radial arms. Finally, the resulting frame forms a single piece that cannot be taken apart, thereby complicating maintenance operations of the turbomachine.